134 research outputs found
Comparison of Vlasov-Uehling-Uhlenbeck model with 4 π Heavy Ion Data
Streamer chamber data for collisions of Ar + KCl and Ar + BaI2 at 1.2 GeV/nucleon are compared with microscopic model predictions based on the Vlasov-Uehling-Uhlenbeck equation, for various density-dependent nuclear equations of state. Multiplicity distributions and inclusive rapidity and transverse momentum spectra are in good agreement. Rapidity spectra show evidence of being useful in determining whether the model uses the correct cross sections for binary collisions in the nuclear medium, and whether momentum-dependent interactions are correctly incorporated. Sideward flow results do not favor the same nuclear stiffness parameter at all multiplicities
Possible tetraquark states in the invariant mass distribution
In this article, we assume that there exist hidden charmed tetraquark states
with the spin-parity , and calculate their masses with the QCD sum
rules. The numerical result indicates that the masses of the vector hidden
charmed tetraquark states are about or
, which are inconsistent with the experimental
data on the invariant mass distribution.
The hidden charmed mesons , or may be scalar hidden charmed
tetraquark states, hadro-charmonium resonances or molecular states.Comment: 12 pages, 4 figure
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Search for the Xb and other hidden-beauty states in the π+π−ϒ(1S) channel at ATLAS
This Letter presents a search for a hidden-beauty counterpart of the X(3872) in the mass ranges of 10.05–10.31 GeV and 10.40–11.00 GeV, in the channel Xb→π+π−ϒ(1S)(→μ+μ−), using 16.2 fb−1 of pp collision data collected by the ATLAS detector at the LHC. No evidence for new narrow states is found, and upper limits are set on the product of the Xb cross section and branching fraction, relative to those of the ϒ(2S), at the 95% confidence level using the CLS approach. These limits range from 0.8% to 4.0%, depending on mass. For masses above 10.1 GeV, the expected upper limits from this analysis are the most restrictive to date. Searches for production of the ϒ(13DJ), , and states also reveal no significant signals
Nanocrystalline layer on the bearing surfaces of artificial hip implants induced by biotribocorrosion processes
Orthopedic prostheses are lubricated by a pseudosynovial fluid that contains proteins. Under regular movements, bearing surfaces would suffer wear and corrosion. More importantly, their interaction controls the material degradation process. Nanocrystalline layer was found on the surface of CoCrMo alloy surface after tribocorrosion tests. Tribocorrosion tests were taken in 0.9% NaCl and 0.9% NaCl with 1% bovine serum albumin (BSA) solution. Small angle X-ray Scattering was applied to measure the size distribution of the nano-crystals. As a general conclusion, proteins can absorb on prosthesis materials and act as a lubricant during sliding. The negative charge distribution on the material surface can promote the adsorption of protein. The average size of the nano-crystals on the bearing surface was 5 nm
Hydrogen-facilitated corrosion and stress corrosion cracking of austenitic stainless steel of type 310
Surface preparation effect on duplex stainless steel passive film electrical properties studied by in situ CSAFM
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